This report describes the study of regional flood frequency analysis using peak flood series data of gauging stations of Krishna basin based on at site and regional data combined using the following methods: (a) Index-Flood method (b) PWM based EVI distribution (c) PWM based GEV distribution and (d) PWM based Wakeby distribution.
The estimation of the extreme flood at a site is required for the design of a variety of urban planning and river engineering works. An accurate estimation of extreme flows for the associated recurrence interval is difficult to obtain if the length of the available stream flow records at the site of concern is shorter than the recurrence interval of interest. An even greater difficulty occurs if there is no flow record available at the site of interest.
The problem arising due to an insufficient length of data record can be addressed by a trade-off between the spatial and temporal characterization of extreme flows through the use of regional flood frequency analysis. Regional flood frequency analysis facilitates the estimation of an extreme flow value at a location for which limited flow data exists based on an extreme flow relationship derived using the information from basins with similar hydrologic responses.
The United States Geological Survey’s (USGS) homogeneity test was used to omit 6 sites out of 34. Of the remaining 28 sites, 26 were considered for analysis under 3 different sub-groups i) medium catchment ii) large catchments and iii) considering the basin as whole. In order to evaluate the fitting performance of different methods used, some of the error functions and their descriptive ability are computed.
The results indicate that, the Index-Flood approach and PWM based EVI distribution are best suited for medium catchments for the basin as whole. However, it is recommended to include the other physiographic characteristics as well for developing a more rational regional flood formula using a good database.
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